linux-kernel - Re: [PREEMPT-RT] Oops in rapl_cpu

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Date:   Fri, 28 Oct 2016 10:03:24 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     "Charles (Chas) Williams" <ciwillia@...cade.com>
Cc:     linux-kernel@...r.kernel.org, rt@...utronix.de
Subject: Re: [PREEMPT-RT] Oops in rapl_cpu_prepare()

On 2016-10-27 15:00:32 [-0400], Charles (Chas) Williams wrote:
> > I assume "init_rapl_pmus: maxpkg 4" is from init_rapl_pmus() returning
> > topology_max_packages(). So it says 4 but then returns 65535 for CPU 2
> > and 3. That -1 comes probably from topology_update_package_map(). Could
> > you please send a complete boot log and try the following patch? This
> > one should fix your boot problem and disable RAPL if the info is
> > invalid.
> 
> But sometimes the topology info is correct and if I get lucky, the
> package id could be valid for all the CPU's.  Given the behavior,
> I have seen so far it makes me thing the RAPL isn't being emulated.
> So even if I did boot onto a "valid" set of cores, would I always be
> certain that I will be on those cores?

I don't what vmware does here. Nor do they ship source to check. So if
you have a big HW box with say two packages, it might make sense to give
this information to the guest _if_ the CPUs are pinned and the guest
never migrates.

> Per your request in your next email:
> 
> > One thing I forgot to ask: Could you please check if you get the same
> > pkgid reported for cpu 0-3 on a pre-v4.8 kernel? (before the hotplug
> > rework).
> 
> Our previous kernel was 4.4, and didn't use the logical package id:
I see.

Did the patch I sent fixed it for you and were you not able to test?

Sebastian